Project One will examine the hypothesis that estrogen receptor (ER) and epidermal growth factor receptor (EGFR) activate proliferative signaling pathways in non-small cell lung cancer (NSCLC), and that these signaling pathways overlap and interact. Based on results obtained in the first SPORE grant period, we hypothesize that ER expression and signaling have functional significance in NSCLC and that co-inhibition of ER and EGFR may show greater anti-tumor activity in NSCLC than inhibition of either pathway alone. Data obtained in the first SPORE grant period suggest that there may be some sex differences in the ER pathway in lung cancer, but that the ER pathway is also active in males. We will carry out this translational research project targeting the ER and the EGFR in four specific aims: (1) Determine signaling molecules involved in ER-EGFR pathway interactions in NSCLC cell lines; (2) Examine effectiveness of joint inhibition of the EREGFR pathways on tumor growth compared to single therapy in NSCLC, using clinically relevant agents; (3) Determine if aromatase, the enzyme that synthesizes estrogen, is present and functional in normal and malignant lung cells and if an aromatase inhibitor has anti-tumor activity; and (4) Analyze ER and EGFR pathway status in tissues obtained from NSCLC patients on clinical trials using combination therapy. Results from these aims will demonstrate how the ER and EGFR signaling pathways interact and to what extent ligand-dependent and ligand-independent ER signaling play a role in NSCLC proliferation. Results will also determine whether inhibition of estrogen synthesis is a potentially effective therapeutic strategy for NSCLC. Results will further demonstrate how responses to combined ER and EGFR targeting in a clinical trial are related to ER and EGFR signaling pathways in patients' tumors and whether combined therapy gives superior clinical responses compared to targeting EGFR alone. We will also determine to what extent EGFR with mutation in the tyrosine kinase domain differs from wild type EGFR in the integration of the ER and EGFR pathways. Completion of these aims will provide a new paradigm for treatments targeting the ER in NSCLC that could be applied to both men and women with this disease.